Zeratul was allowed to flee after Kerrigan saw that he killed his own Matriarch. On his desperate quest to find Artanis, he finds an energy signature on an uncharted Dark Moon, and hopes Artanis or other Protoss survivors are there. Zeratul is in for a big surprise...

By completing Zerg Mission 9 (The Reckoning) with 5 minutes or more left on the timer, this secret mission is unlocked.

You start with two dragoons, Zeratul, and FOUR dark archons. With this force, you need to escort Zeratul to each beacon/stasis cell, revealing some ominous foreshadowing along the way. Destroy the stasis cells as you come to them, as they contain Protoss units (or Zerg, but they're easy to deal with). However, the one near the center of the map contains an Infested Terran who will blow up in your face, so be careful.

Anyway, as you move along the map, use Zeratul to scout and then mind control any high-value targets. Those two Siege Tanks at the start will do nicely, as will a nearby Science Vessel. There are several Science Vessels around the map, so use them to scout, irradiate infantry, and defend more valuable units. Move cautiously through the Terran base, using your Siege tanks to strike at range. Play cautiously, as you can't easily get replacements, and steal an SCV to repair your stolen units. Finally, prioritize Science Vessels and Missile Turrets. If they are destroyed, you can send in Zeratul to single-handedly slaughter the enemies. Don't bother mind-controlling the isolated infantry, just blast them off the map with your tanks. In the final area, resistance is thick with Battlecruisers and Siege Tanks, but if you slowly advance your Siege Tanks and use Science Vessels to scout, you'll break through. This mission is relatively easy, but if you fritter away your units (particularly your essential Dark Archons) it becomes painful.

Once you reach the last beacon, you win, though you'll have more questions than when you started.